Но так как продолжительность жизни

Но так как продолжительность жизни тоже упала из-за низкой рождаемости и высокой смертности, то население уменьшилось, и вскоре уровень жизни вернулся к прежней Невысокой норме

Результаты (английский) 1:

But because life expectancy also dropped due to low fertility and high mortality, the population declined, and soon returned to their former living standards Low norm

Результаты (английский) 2:

But as life expectancy also fell due to the low birth rate and high death rate, the population decreased, and soon returned to the standard of living is still low rate of

Результаты (английский) 3:

but since life expectancy also fell because of the low birth rate and high mortality, the population decreased, and soon returned to the same low level of life.